Edexcel IGCSE Math A 1.8.D estimation for numerical calculations

Practise estimation questions by rounding every number first and using the simplified calculation to judge whether an answer is sensible.

Exam points

Round each number to 1 significant figure before estimating products, divisions or roots.
Compare an approximate result with a calculator answer to decide whether it is sensible.

[Maximum number: 2]

The weight of a cake is 2.75 kg , correct to 2 decimal places.

By rounding each number to one significant figure, work out a suitable estimate to show that her answer is not sensible.
Show your working clearly.

Rounded estimate:
$\frac{80\times60}{2^{2}}=\frac{4800}{4}=1200$
Final estimate:
1200
Working with rounded values must be seen.

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